The overall objective is to develop a series of data on which assessment of potential health consequences, especially total burden of environmental carcinogens and mutagens, resulting from combustion of fossil fuels can be made more objectively and with greater precision than is currently possible. The general approach is to define conditions of combustion for several fuel types, including readily vaporized fuel, coal, heavy oil and shale oil, which generate minimal amounts of compounds with carcinogenic and/or mutagenic properties. Several approaches utilized involve the collaboration of combustion engineers, analytical chemists, and biologists. Lines of investigation include: (1) Parametric studies conducted on small scale burners to determine effects of temperature, equivalence ratio and fuel type on the formation of organic and inorganic particulates; (2) selected samples from the combustion experiments subjected to chemical analysis using GC-MS for soot extracts and size fractionation, neutron-activation analysis and surface characterization for inorganic particulates; (3) evaluations of biological and biochemical properties of selected samples produced under defined combustion conditions with respect to mutagenicity in bacteria and human cells and ability to form covalent adducts with nucleic acids when activated in vitro and in vivo; (4) selected samples produced by combustors operated under conditions defined in small-scale burners and preliminary biological experiments, characterized chemically and biologically.